The present invention relates generally to voltage regulators, and more particularly to a switching voltage regulator at least partially implemented with flip-chip packaging.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones. Switching voltage regulators (or simply "switching regulators") are known to be an efficient to type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency voltage to generate the output DC voltage. Specifically, the switching regulator includes a switch for alternately coupling and decoupling an input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, between the input voltage source and the load filters the output of the switch and thus provides the output DC voltage. The switch is typically controlled by a pulse modulator, such as a pulse width modulator or a pulse frequency modulator, which controls the switch.
Switching regulators are now being fabricated at least partially with integrated circuit techniques. Specifically, some switching regulators are being fabricated in integrated circuit chips with wire bond packaging (in which wires extend from the sides of the chip to the package, and the package has leads that are soldered to a printed circuit board). Unfortunately, one problem with wire bond chips is that they have a large parasitic inductance and resistance.
The parasitic inductance can result in large voltage transients on the integrated circuit. Specifically, although there is an abrupt change in the supply current when switching from the high to low voltage inputs, the current flowing through the parasitic inductor cannot change instantaneously. Thus, some current will continue to flow, causing the voltage on the voltage supply lines to "bounce". If the voltage transients exceed the process limitations of the integrated circuit, there can be damage due to voltage overstress. In addition, if the voltages on the voltage supply lines come too close together or cross, the digital and analog circuitry in the voltage regulator will fail. Furthermore, large voltage transients create noise which can interfere with the normal operation of analog components of the power regulator. Compensating for this noise requires additional circuitry, at the expense of design time, silicon area and power consumption.
The parasitic resistance of the packaging increases energy dissipation, which wastes energy and creates excess heat. This excess heat can degrade circuit performance, and in order to avoid the degraded circuit performance, it is necessary to use expensive heat sinks or cooling systems, or limit the current flowing through the device.
In view of the foregoing, it would be advantageous to develop a switching regulator with reduced parasitic inductance and resistance.